In hydraulic steering systems used for automobiles and light duty trucks, a cylinder is used in cooperation with a piston to control the steering fluid. Because of the high pressures that sometimes occur to the steering system, a reliable seal is needed between the cylinder and the piston resulting in very close tolerances on the interior of the cylinder where the piston travels. One end of the tube has traditionally been closed by welding a cap into the end.
While this prior design has been used successfully, it has several disadvantages, particularly in the fabrication process. During the fabrication process, the prior method of fabricating the cylinder is relatively labor intensive in that it requires the positioning of the separate end cap piece within the high tolerance cylinder and holding it in position during welding. In addition, by requiring the second piece, i.e., the end cap to be joined to the cylinder during fabrication, it increases the likelihood of contamination being carried by the end cap into the cylinder. This is particularly of concern in that if any metal cylinders or other contamination marred the interior central portion of the cylinder where the piston is to travel, the seal between the piston and the sides of the cylinder may not sufficiently exist to allow for adequate operation.
Also, since the joining of the cap to the cylinder requires a complete 360.degree. weld, the welding process must be very precise and despite this, testing often indicates that failure under high pressure most often occurs in this area.